Straightening and cutting-off machine

ABSTRACT

A straightening and cutting-off machine for the production of straightened elements of predeterminable length from a wire-shaped material, in particular for the production of straightened bars from reinforced-concrete steel wire, has a feed device for drawing in material from a material stock, a preferably rotating straightening device for straightening the material conveyed into a working range of the straightening device by the feed device, a cutting device, following the straightening device, for separating a portion of predeterminable length from the straightened material to produce the straightened element, a length measurement system for measuring the length of the material and for generating a measurement signal representing the length, and a control device for activating the cutting device on the basis of the measurement signal. The measurement system is a contactlessly operating optical measurement system, in particular a laser measurement system, which allows length measurement continuously with high measurement accuracy even at high run-through speeds.

RELATED APPLICATION

This application claims priority of German Patent Application No. 102010 014 384.7, filed on Apr. 6, 2010, the subject matter of which isincorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to straightening and cutting-off machines forthe production of straightened elements of predeterminable length from awire-shaped material, in particular for the production of straightenedbars from reinforced-concrete wire.

BACKGROUND

Straightening and cutting-off machines, which are also occasionallydesignated as straightening and cutting-to-length machines or simply asstraightening machines, are designed to straighten wires and othermaterials processable by straightening and having differentcross-sectional sizes and shapes and cut them off to a desired length.Thus, for example, ribbed wires consisting of reinforced-concrete steelcan be processed into straightened bars which are subsequently weldedtogether in a net-like manner to form reinforced-concrete steel mats forreinforcing concrete structures. Unribbed smooth wires can also beprocessed, for example, to obtain straightened wire bars for theconstruction of cages, shopping trolleys, fences, baskets or the like.

A known straightening machine has a feed device for drawing in thematerial to be straightened from a material stock, a straighteningdevice for straightening the material conveyed by the drawing-in deviceinto a working range of the straightening device, and a cutting device,following the straightening device, for separating a portion ofpredeterminable length from the straightened material to produce thestraightened element. The material is usually present on a wire spindle(coil), is unwound from the wire stock by push rollers of the feeddevice and is led into the straightening device where the wire, stillhaving stresses and bends, is straightened. Thereafter, the thenstraightened material is drawn out of the straightening device by drawrollers on the feed device and conveyed in the direction of what may bereferred to as an “add-on.” When the desired length is reached in thestraightened material portion, the portion is cut off with the aid ofthe cutting device and falls into a collecting trough. Straightenedelements having a great length of several meters or several tens ofmeters and having low length tolerances can be produced.

The cut by which the straightened element is separated from the materialmust take place at the correct time point or at the correct location ofthe conveyed material to obtain the desired length with the desiredaccuracy. For this purpose, a straightening and cutting-off machine hasa length measurement system that measures the length of the movedmaterial and generates a measurement signal which represents the lengthand which is then processed by a control device to activate the cuttingdevice. Various measurement methods are employed nowadays for lengthmeasurement.

A known method works with the aid of a measuring wheel, thecircumference of which is pressed onto the material running through suchthat the measuring wheel is driven by the material and co-rotates withit. The shaft of the measuring wheel transmits the rotational movementto a rotary encoder, the encoder signals of which are processed forindirect length measurement. To prevent slip between the measuring wheeland the moved material, a running wheel is pressed against the materialfrom the opposite side, with the result that the material is tensionedbetween the measuring wheel and the running wheel. The configuration ofthe measuring wheel may vary, depending on the material to bestraightened. In the straightening of ribbed structural steel, forexample, a measuring wheel having teeth on the circumference is normallyemployed to achieve the best possible take-up. Where smooth materialsurfaces are concerned, measuring wheels having a smooth circumferentialface are occasionally used, especially when the surface of the materialrunning through should not be damaged. In some configurations, toenlarge the pressure area, a continuous groove is introduced into thecircumference of the measuring wheel, with the result that slip betweenthe measuring wheel and material can be reduced.

Length measurement with the aid of a measuring wheel is a structurallysimple and robust measurement method. When measuring wheels are used,however, it must be remembered that, after a certain period of use,measurement accuracy may gradually become lower due to wear on themeasuring-wheel circumference. Relatively frequent calibration orexchange of measuring wheels is therefore recommended. Furtherinaccuracies or measurement errors may arise due to insufficientfriction between the material and measuring wheel, that is to say due toslip. Although it is possible to mitigate this problem by increasing thepressure force, this usually has an adverse effect upon the wear whichmay lead, in turn, to measurement inaccuracies after lengthy use.

Another possibility of length measurement is to use a manuallyadjustable trigger head in the add-on. In this method, triggering of thecut takes place via the trigger head which is fixed in a suitableposition on a carrying rail of the add-on, depending on the desiredlength of the straightened element. For this purpose, as a rule, a scalefastened to a guide element of the add-on is used. When the free frontend face of the straightened material impinges onto a trigger leverduring feeding, the latter pivots out of the path of movement of thematerial and triggers the cut via a signal. The trigger head may alsocontain a stop which is mounted at a short distance behind the contactface of the trigger lever. In these instances, during triggering of thecut, the element impinges onto the stop to achieve as exact a length aspossible. Since, in length measurement by a manually adjustable triggerhead, length measurement takes place only very shortly before the cut,the distance over which measurement errors can still arise is very shortand, therefore, very high measurement accuracies can be achieved. Lengthtolerances when a stop is used may lie in the range of a few tenths of amillimeter and, without a stop, tolerances of the order of one to twomillimeters are usually achieved. Although the measurement method with atrigger head is accurate, setting up a new desired length is relativelycomplicated and requires operator experience. Variants with a stopshould not be used in machines with a rotating cut since material isotherwise pushed onto the stop during cutting.

It could therefore be helpful to provide a straightening and cutting-offmachine which is capable of producing, in continuous operation, and at ahigh production rate, straightened elements having very low deviationsfrom the desired length. It could also be helpful to enable a changeoverto other desired lengths with only little effort and provide thatprecision in length setting depends as little as possible on theoperator's experience.

SUMMARY

We provide straightening and cutting-off machines that producestraightened elements of predeterminable length from a wire-shapedmaterial including a feed device that draws in material from a materialstock, a straightening device that straightens the material conveyedinto a working range of the straightening device by the feed device, acutting device, following the straightening device, that separates aportion of a predeterminable length from the straightened material toproduce the straightened element, a contactlessly operating lengthmeasurement system that measures length of the material and generates ameasurement signal representing the length, and a control device thatactivates the cutting device on the basis of the measurement signal.

We also provide straightening and cutting-off machines that producestraightened elements of predeterminable length from a wire-shapedmaterial including a feed device that draws in material from a materialstock, a straightening device that straightens the material conveyedinto a working range of the straightening device by the feed device, acutting device, following the straightening device, that separates aportion of predeterminable length from the straightened material toproduce the straightened element, a length measurement system thatmeasures length of the material and generates a measurement signalrepresenting the length and includes a laser measurement system having adevice that generates at least one laser beam directed onto the materialand devices that detect interaction between the laser beam and a surfaceof the material, wherein the laser beam impinges onto the surface of thematerial from above such that an angle between a radial direction to arun-through direction of the material and a radiation direction is lessthan about 30°, and a control device that activates the cutting devicebased on the measurement signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a general illustration of an example of a straightening andcutting-off machine for the production of straightened bars fromreinforced-concrete steel from the operator side.

FIG. 2 shows a detail of the straightening machine shown in FIG. 1, witha measuring head, arranged between draw rollers and a rotating cuttingdevice, of a laser Doppler measurement system.

FIG. 3 shows a view of the measuring head, shown in FIG. 2, from adirection parallel to the run-through direction of the straightenedmaterial.

DETAILED DESCRIPTION

It will be appreciated that the following description is intended torefer to specific examples of structure selected for illustration in thedrawings and is not intended to define or limit the disclosure, otherthan in the appended claims.

We provide straightening and cutting-off machines for the production ofstraightened elements of predeterminable length from a wire-shapedmaterial comprising: a feed device for drawing in material from amaterial stock; a straightening device for straightening the materialconveyed into a working range of the straightening device by the feeddevice; a cutting device, following the straightening device, forseparating a portion of predeterminable length from the straightenedmaterial to produce the straightened element; a length measurementsystem for measuring the length of the material and for generating ameasurement signal representing the length; and a control device foractivating the cutting device on the basis of the measurement signal;wherein the measurement system is a contactlessly operating measurementsystem.

In our straightening and cutting-off machines, the measurement system isa contactlessly operating measurement system. A contactlessly operatingmeasurement system is capable of ensuring length measurement or speedmeasurement of the material running through in a run-through directionwithout touch contact occurring between an element of the measurementsystem and the material running through. As a result, inter alia, wearof measuring elements and possible slip between the moved material and ameasuring element may be avoided. A contactless measurement system canoperate continuously, free of wear, so that measurement accuracy doesnot depend on the period of use. Wear-induced maintenance or repair workis also avoided. The measured material is protected.

Preferably, the measurement system is an optical measurement system,that is to say a measurement system in which light from a suitablewavelength range of the electromagnetic spectrum is used for themeasurement and evaluation of the movement of the material. In thiscase, the interaction of light from the visible wavelength range or fromadjacent wavelength ranges of the spectrum with the moved material isdetected and evaluated with the aid of optical systems and opticaleffects. Contactless measurements of high accuracy are possible hereeven in the case of high speeds of movement of the moved material.

Comprehensive investigations have shown that, in light of the variousboundary conditions in straightening and cutting-off machines, it isusually especially advantageous if the measurement system is a lasermeasurement system which has a device for generating at least one laserbeam directed onto the material and devices for detecting theinteraction between the laser beam and a surface of the material. Forexample, laser distance measurement may be employed in which a laserbeam is directed essentially coaxially to the moved material, onto anend face of the material. The orientation of the measuring beam involvesa relatively high outlay and measures for reducing the sensitivity ofthe measurement system to dust and dirt should be taken.

It has proven substantially more beneficial if the measurement system isset up in such a way that the laser beam impinges onto the surface ofthe material in a radiation direction running transversely with respectto a run-through direction of the material. The radiation direction canthen, for example, be in the radial direction to the run-throughdirection or at an acute angle thereto. An essentially radial radiationof the laser beam may be advantageous because, as a rule, only littleaxial construction space is then required for those components which areneeded directly for generating the laser and guiding its beam anddetecting the laser radiation after interaction with the material sothat integration into straightening and cutting-off machines is possiblein a simple way. As exact a radial radiation as possible may bebeneficial in some examples to obtain high measurement accuracy. Ifdeviations from radial radiation are present, these should be low.Preferably, an angle between a radial direction to the run-throughdirection and the radiation direction amounts to less than about 30°, orless than about 20°, or less than about 10°, or less than about 5°.

As an alternative to a laser measurement system, optical measurementsystems can also be used which, for example, operate according to theCCD spatial-filter method or according to the grid transmitted-lightmethod.

It has proven especially advantageous if a laser measurement system isused which operates according to the laser Doppler principle. With asuitable design, maximum measurement accuracies for a multiplicity ofdiameters of the material of, for example, approximately 0.5 mm to 30 mmor more and for most movement speeds typically occurring instraightening and cutting-off machines (typically of between about 3m/min and about 400 m/min) can be achieved. The laser beam emanatingfrom a laser is in this case broken down with the aid of a beam splitterinto two coherent part-beams which are projected obliquely to oneanother onto a region of the measurement object, are superposed thereand generate in the superposition region a system of interferencefringes. Particles or structures on the surface of the measurementmaterial scatter the light when it passes through the bright fringes. Adetector receives this scattered light which is modulated with a Dopplerfrequency from which the speed of the scatter centers and, therefore,also the speed of the irradiated surface can be determined. The lengththat has run through can be determined by integrating the speed.

A frequency shift may be generated between the two transmission beams ofthe laser Doppler measurement system so that a movinginterference-fringe system is obtained. It is thereby possible, interalia, to measure with high precision even up to the standstill of themeasurement object.

When a contactless measurement system is integrated into a straighteningand cutting-off machine, numerous boundary conditions must be taken intoaccount, operator safety also playing a major part in the use of a lasermeasurement system. Typically, the straightening and cutting-off machinehas an operator side and an operator-remote side, while criticalcomponents of the machine should be accessible from the operator sidefor maintenance, repair and setting-up work, and the drives are normallyarranged on the operator-remote side. Preferably, the measurement systemis set up in such a way that the laser beam impinges onto the materialfrom the operator side, thus ensuring that the eyes of operators aresafe. To ensure that the operation of the machine is not impaired bycomponents of the measurement system, the operator side should, at leastin the region of the material run-through, be free of components of themeasurement system. Preferably, the run-through direction of thematerial lies in a vertical plane, and the measurement system is set upin such a way that a radiation direction of the laser beam forms withthe vertical plane an angle of less than about 45°, in particular ofless than about 20°, the laser beam preferably impinging onto thematerial from above.

In a laser-based measurement system, the laser beam should impinge ontothe moved material continuously as far as possible without interruptionsso that measurement signals can be generated constantly or at very highfrequency. Special conditions prevail in this respect in straighteningand cutting-off machines. In the straightening device, the materialrunning through is formed mechanically in a plurality of directionsrunning obliquely with respect to one another to achieve the desiredstraightening action. Preferably, the straightening device has astraightening mechanism which rotates during operation and by means ofwhich it is possible to straighten the material in all planes. Themechanical engagement of the straightening device on the material maygive rise in the latter to stresses, in particular also torsionalstresses, which are occasionally discharged in a jolt-like manner duringfurther transport of the material. This may lead to an unsteady run ofmaterial and to associated measurement errors if no countermeasures aretaken.

Preferably, the feed device has a pair of draw rollers arrangeddownstream of the straightening device and rotatable contradirectionallyabout parallel axes of rotation, and a measuring head of the measurementsystem is arranged between the draw rollers and the cutting device. Thedraw rollers preferably have a concave circumferential contour or acontinuous groove, so that, in the region of their greatest approach toone another, they provide a guide orifice for the straightened materialwith certain lateral guidance. If torsional stresses within the wire areto be reduced, the wire can rotate slightly within the guide orifice,with the result that the material is relaxed by slip in thecircumferential direction. Since lateral movement of the material isgreatly limited directly downstream of the draw rollers, it isespecially beneficial to direct the measurement radiation onto thematerial in this region, since the material cannot shift away laterallythere.

As a rule, one of the draw rollers is mounted fixedly with respect tothe machine, whereas the other draw roller can be displaced in alifting-off direction running perpendicularly with respect to the axisof rotation, counter to the force of a press-down device which, forexample, operates pneumatically. This maneuvrability of one axis ofrotation makes it possible that the movably mounted draw roller canshift away in the lifting-off direction when thickenings, ribs, dirtand/or other irregularities run through the guide orifice of the drawrollers. Since, in such instances, there is a certain latitude parallelto the lifting-off direction for the material, preferably themeasurement system is set up in such a way that a radiation direction ofthe at least one laser beam forms with the lifting-off direction anangle of less than about 45°, in particular of less than about 20°, thelaser beam preferably impinging onto the material from above. What canbe achieved thereby is that the laser beam remains on the material evenwhen the latter lifts off in the lifting-off direction. Measurementerrors on account of irregularities of the material can thereby beavoided. By a measuring head of the measurement system being arrangedabove the run-through direction, the situation can also be preventedwhere optical components and/or sensors of the measurement systemquickly become soiled, so that low-maintenance continuous operation ispossible.

This and further features may also be gathered from the description andthe drawings, as well as from the appended claims, while the individualfeatures can in each case be implemented individually or severally inthe form of subcombinations in selected examples and in other fields andcan constitute advantageous structures. Representative examples areillustrated in the drawings and are explained in more detail below.

FIG. 1 shows a general illustration of an example of a straightening andcutting-off machine 100 for the production of straightened elements ofpredeterminable length from a wire-shaped metallic material 105. Themulti-axial CNC machine tool, also designated below simply as a“straightening machine” 100, is designed for the production ofstraightened bars from ribbed reinforced-concrete steel wire. Wires ofthis type typically have diameters of between about 3.5 mm and about 30mm, where appropriate even with other diameters. The straightenedreinforced-concrete steel wire elements cut to the correct length arerequired in large quantities for the production of reinforced-concretesteel mats which are used as reinforcing elements for concretestructures. If the straightened reinforced-concrete steel bars producedare too short, this may lead, when the net-like reinforced-concretesteel mats are being produced, to unconnected places betweenlongitudinal and transverse bars and therefore to a weakening of thestructure. If the bars are too long, problems arise in the handling ofthe structural-steel mats. Narrow length tolerances must therefore beadhered to for the straightened bars.

The straightening machine is capable, in the case of high materialthroughput and run-through speeds of up to about 160 m/min or more,where appropriate even of up to about 360 m/min or about 400 m/min, ofproducing large quantities of such straightened elements with a lengthof, where appropriate, several meters, and with a very low length errorin the per-thousand range or below.

The wire-shaped material is initially present on a large wire coil andis drawn off from the material stock with the aid of a feed device andconveyed into the straightening machine. The feed device has, on theentry side of the straightening machine, two pairs, arranged one behindthe other, of push rollers 112, 114 which draw off the wire from thematerial stock and convey it in the direction of the straighteningdevice 120 following in the run-through direction 102. The straighteningdevice serves for straightening the material conveyed into the workingrange of the straightening device by the push rollers and for thispurpose has a rotary-driveable straightening wing 122 with a pluralityof lead-through orifices for the material which are arranged at an axialdistance one behind the other and are offset radially with respect toone another. Such rotating straightening systems are known per se andare therefore not explained in any more detail here.

Directly downstream of the straightening device is arranged a pair ofdraw rollers 116 which belong to the feed device of the straighteningmachine and draw the straightened material out of the straighteningdevice. Mounted at a distance downstream of the draw rollers is acutting device 130 which follows the straightening device and which isintended for separating portions of predeterminable length from thestraightened material to produce the straightened elements ofpredeterminable length.

The cutting device 130, which can be seen especially well in FIG. 2, isdesigned for a rotating cut so that, during the cutting operation, thematerial can run uniformly through the rotating straightening wing andthe cutting device without a feed interruption. In a straighteningmachine with rotating shears, the wire is severed without being brakedand without a wire standstill. The cutting operation in this caseconsists of various phases. First, the cutting-tool carriers 132, 134driveable contradirectionally in rotation are accelerated such thattheir circumferential speed corresponds at least to the wire speedduring engagement of the cutting tools 133, 135 on the wire. After asuitable speed is reached, the wire is severed as a result of thepenetration of the cutting tools. This situation is shown in FIG. 2.During cutting, the cutting tools move even more quickly than the wireso that, by means of the cut, the severed bar is thrown away forwardsand a gap with respect to the following wire occurs.

The cutting tools are then moved into their initial position again sothat the rotating cutting-tool carriers execute one revolution per cut.In cutting without wire standstill, the rib abrasion in the region ofthe draw rollers can be minimized. Moreover, no non-uniform structuralvariations occur in the material in the region of the straighteningdevice since each portion of the material experiences the same formingaction in the region of the straightening device.

On the exit side of the straightening machine is located what is knownas the add-on 140 with a guide chute into which the straightenedelements are pushed. When the set length is reached, the wire is cut offand falls into a collecting trough 150. This basic construction may beused for different lengths.

Straightened elements consisting of reinforced-concrete steel wiretypically have a length of several meters and may, for example, be up toabout 25 m long. However, shorter elements can also be produced by thesame principle.

To achieve the desired length of the straightened elements with highaccuracy, a length measurement system is provided for measuring thelength of the material and generating a measurement signal representingthe length. The measurement signal is processed by a computer-basedcontrol device, not illustrated in any more detail, of the straighteningmachine for the purpose of activating the cutting device 130 to generatea correctly positioned cut.

A contactlessly operating measurement system in the form of a lasermeasurement system which operates according to the laser Dopplerprinciple may be provided. Mounting details are illustrated in FIGS. 2and 3, FIG. 2 showing an enlarged detail of the straightening machine inthe region of the measuring head 182, and FIG. 3 showing a view in therun-through direction of the wire towards the exit side of the drawrollers 116 which faces away from the straightening device.

A measuring head 182 of the laser measurement system is mounted abovethe run-through direction of the wire directly downstream of the drawrollers 116 between the draw rollers 116 and the cutting device 130. Themeasuring head is fastened to the front side, facing the draw rollers,of a vertical intermediate wall 189 mounted fixedly with respect to themachine approximately centrally between the draw rollers 116A, 116B andthe cutting device 130, that is to say nearer to the draw rollers thanto the cutting device. The intermediate wall serving as a carrier forthe measuring head has a passage orifice for the material 105. Theposition of the measuring head on the intermediate wall 189 can be setvia adjusting screws.

The measuring head 182 accommodates a laser which generates a laserbeam. The laser beam is broken down with the aid of a beam splitter intotwo part-beams which are radiated onto the surface of the wire with theaid of transmission optics as transmission beams 183, 184 runningobliquely with respect to one another. The bisector between thetransmission beams defines the sensor longitudinal axis which should beoriented as perpendicularly as possible to the wire surface serving as ameasurement surface and, consequently, as exactly as possible radiallywith respect to the central axis of the wire or to the run-throughdirection. The working distance between the beam exit face of themeasuring head and the wire surface is approximately 200 mm. This shortworking distance is advantageous so that the split laser beam reliablyimpinges onto the wire surface even in the event of vibrations of theapparatus. The geometry of the arrangement is in this case such that thecoherent transmission beams overlap one another in the region of thenarrow curved surface of the monitored wire material 105 running throughin an overlap region 185 (see the detail). In this region (measurementvolume), a system of alternating light and dark interference fringesoccurs, with a fringe spacing defined by the wavelength of thetransmission beams (here, in the red part of the visible spectrum) andthe angle between them. Scatter centers on the material surface, forexample particles or certain surface roughness, run through this fringesystem and scatter the light when it passes through the light fringes. Adetector 186 receives this scattered light which is modulated with aDoppler frequency which is proportional to the speed component of thematerial in the run-through direction. The length that has run throughcan be determined by integrating the speed over time. This measurementmethod is not impaired by the ribs on the wire surface and isindependent of the rib shape. In straightening machines with a rotatingcut and with a material correspondingly running through continuously,simple and robust measurement systems of this type can advantageously beemployed.

The laser light coming from a laser diode may be broken down into twopart-beams by an optoacoustic modulator in the form of a Bragg cell. TheBragg cell not only splits the laser beam, but also generates in one ofthe two part-beams a frequency shift with respect to the otherpart-beam, thus giving rise in the overlap region to a system of runninginterference fringes. It is thereby possible both to determine the signof the movement speed and measure it during a material standstill.Measurement accuracies for the run-through speed in the region of about1 mm/min or below are regularly achievable. In particular, precisemeasurement is also possible in examples with a standing cut.

The two part-beams 183, 184 define a radiation plane 188 in which thesensor longitudinal axis (bisector between the part-beams) also lies. Ascan be seen clearly in FIG. 3, radiation onto the wire 105 takes placeobliquely from above in such a way that the radiation plane 188 formswith a vertical plane 108 running through the wire 105 an angle 185 ofless than about 20°, in the example of about 16°. As a result, the laserlight emanating from the measuring head cannot pass directly into anoperator's eyes and, therefore, eye safety is afforded. Even in the caseof reflecting measurement-object surfaces, there will still be eyesafety since the reflected radiation is be directed away from theoperator side towards the operator-remote side. Furthermore, owing tooblique illumination from above, the region of the measurement location(overlap region 185) directly downstream of the draw rollers is easilyaccessible from the operator side and, therefore, possible work in thisregion is not impeded by the measuring head 182. The sensors and opticsof the measuring head are largely protected against soiling by beingarranged above the material running through.

The geometric arrangement is such that the part-beams impinge onto thewire running through at any time in a superposition region, even ifsudden relaxations of the torsional stresses generated in the rotatingstraightening wing and/or the passage of irregularities of material wereto occur in the straightened material. A plurality of structuralmeasures contribute to this.

It can be seen in FIG. 3 that the draw rollers 116 have on theirrespective circumferential faces continuous grooves or a concavecontour, thus giving rise in the region of the greatest approach of thedraw rollers to one another to a more or less circular guide orificewhich provides the material running through with lateral guidanceagainst shifting away sideways. The wire therefore cannot creeplaterally out of the overlap region of the part-beams.

By contrast, minor upward shifting movements are permitted in structuralterms to compensate for irregularities of the material and the like. Forthis purpose, there is provision for the lower draw roller 116A to bemounted in a rotary bearing fixed with respect to the machine, while theupper draw roller 116B is mounted movably such that slight displacementin a vertical lifting-off direction 117 is possible. As a result, theupper draw roller can be raised somewhat such that when the machines arebeing set up, a wire may be introduced between the guide rollers fromthe side. The upper draw roller is pressed in the direction of the lowerdraw roller with the aid of a pneumatically actuable press-down device118, but can briefly be lifted off upwards, counter to the force of thepress-down device, by the material running through. Even thislifting-off movement does not impair measurement, however, since thepart-beams of the laser measurement system are directed onto the middleof the wire essentially from above and still impinge onto this middleeven when the wire is raised upwards slightly.

This ensures continuous contactless optical length or speed measurementwithout measurement gaps, even under the special boundary conditions ofa straightening machine with a rotating straightening system.

Some advantages are explained by an example of a straightening machinefor the production of straightened bars from ribbed reinforced-concretesteel wire. By means of the same or other examples, unribbed structuralsteel and/or wires consisting of other materials from the smooth-wiresector can also be processed. However, straightening and cutting-offmachines are not restricted for the processing of wire materials. Tubesor profiles can also be straightened and accurately cut to length.Depending on the diameter and cross-sectional profile of the material,correspondingly dimensioned components are to be provided for guidanceand straightening.

Other examples with a contactless measurement system may be equippedwith a standing cutting system, that is to say a cutting device withstanding shears. These are often employed in the case of smooth wiresand provide outstanding cutting quality, but normally require a briefwire standstill during cutting.

The above description is directed to preferred examples. From thedisclosure given, those skilled in the art will not only understand ourmachines and their attendant advantages, but will also find apparentvarious changes and modifications to the structures and methodsdisclosed. It is sought, therefore, to cover all changes andmodifications as fall within the spirit and scope of this disclosure, asdefined by the appended claims, and equivalents thereof

1. A straightening and cutting-off machine that produces straightenedelements of predeterminable length from a wire-shaped materialcomprising: a feed device that draws in material from a material stock;a straightening device that straightens the material conveyed into aworking range of the straightening device by the feed device; a cuttingdevice, following the straightening device, that separates a portion ofa predeterminable length from the straightened material to produce thestraightened element; a contactlessly operating length measurementsystem that measures length of the material and generates a measurementsignal representing the length; and a control device that activates thecutting device on the basis of the measurement signal.
 2. The machineaccording to claim 1, wherein the measurement system comprises a devicethat generates at least one laser beam directed onto the material anddevices that detect interaction between the laser beam and a surface ofthe material.
 3. The machine according to claim 2, wherein the lasermeasurement system operates according to the laser Doppler principle. 4.The machine according to claim 2, wherein the laser beam impinges ontothe surface of the material in a radiation direction runningtransversely with respect to a run-through direction of the material. 5.The machine according to claim 4, wherein the laser beam impinges ontothe surface of the material such that an angle between a radialdirection to the run-through direction and a radiation direction is lessthan about 30°.
 6. The machine according to claim 1, wherein thestraightening and cutting-off machine has an operator side and anoperator-remote side, and wherein the laser beam impinges onto thematerial from the operator side.
 7. The machine according to claim 2,wherein run-through direction of the material lies in a vertical plane,and wherein a radiation direction of the laser beam forms with thevertical plane an angle of less than about 45°.
 8. The machine accordingto claim 7, wherein the laser beam impinges onto the surface of thematerial from above.
 9. The machine according to claim 1, wherein thefeed device comprises a pair of draw rollers arranged downstream of thestraightening device and rotatable contradirectionally about parallelaxes of rotation, and a measuring head of the measurement system isarranged between the draw rollers and the cutting device.
 10. Themachine according to claim 9, wherein one of the draw rollers is mountedfixedly with respect to the machine, and another draw roller isdisplaceable in a lifting-off direction running substantiallyperpendicularly with respect to the axis of rotation, counter to theforce of a press-down device, and wherein the measurement systemgenerates a laser beam such that a radiation direction of the laser beamforms with a lifting-off direction an angle of less than about 45°. 11.The machine according to claim 10, wherein the angle is less than about20°
 12. The machine according to claim 10, wherein the laser beamimpinges onto the material from above.
 13. The machine according toclaim 1, wherein the straightening device comprises a rotary-driveablestraightening mechanism.
 14. The machine according to claim 1, whereinthe cutting device comprises a pair of contradirectionally rotatablecutting-tool carriers.
 15. The machine according to claim 1, whichproduces straightened bars from reinforced-concrete steel wire.
 16. Astraightening and cutting-off machine that produces straightenedelements of predeterminable length from a wire-shaped materialcomprising: a feed device that draws in material from a material stock;a straightening device that straightens the material conveyed into aworking range of the straightening device by the feed device; a cuttingdevice, following the straightening device, that separates a portion ofpredeterminable length from the straightened material to produce thestraightened element; a length measurement system that measures lengthof the material and generates a measurement signal representing thelength and comprises a laser measurement system having a device thatgenerates at least one laser beam directed onto the material and devicesthat detect interaction between the laser beam and a surface of thematerial, wherein the laser beam impinges onto the surface of thematerial from above such that an angle between a radial direction to arun-through direction of the material and a radiation direction is lessthan about 30°; and a control device that activates the cutting devicebased on the measurement signal.
 17. The machine according to claim 16,wherein the feed device comprises a pair of draw rollers arrangeddownstream of the straightening device and rotatable contradirectionallyabout parallel axes of rotation, and a measuring head of the measurementsystem is arranged between the draw rollers and the cutting devicedirectly downstream of the draw rollers.
 18. The s machine according toclaim 17, wherein the draw rollers each comprise a concavecircumferential contour so that, in a region of greatest approach of thedraw rollers, a guide orifice with lateral guidance for the straightenedmaterial is formed.
 19. The machine according to claim 17, wherein themeasuring head is fastened to a front side, facing the draw rollers, ofan intermediate wall mounted fixedly with respect to the machine suchthat the measuring head is nearer to the draw rollers than to thecutting device, and the intermediate wall comprises a passage orificefor the material.
 20. The machine according to claim 19, wherein aposition of the measuring head on the intermediate wall can be set viaadjusting screws.